This invention relates generally to electrical magnetic actuators and more specifically to torque motors which may be utilized in the pilot stages of electro-hydraulic or electro-pneumatic valves.
Torque motors are well known in the prior art relating to electro-hydraulic servo-valves as well as to other types of valves used in the direct drive or pneumatic field. Typically, such torque motors are constructed from a pair of pole pieces, an armature, flexural or pivoting means to locate the armature within the torque motor structure, a pair of coils, a pair of magnets and a motor housing. Such torque motors are useful in operating valves and controlling fluid flow of various types and may also be utilized in other applications as well.
In many of the applications involving torque motors, stability and reliability of operation is critical. The ability to operate in extreme temperature cycling conditions of a repetitive nature is also critical as is the resistence to vibration.
Various efforts have been exerted to provide torque motors having the desired reliability and stability and to obtain the operational characteristics as above described. Such techniques as filling spaces in between certain operational components of the torque motor with polymeric fillers, utilizing adhesive materials to retain parts in proper operational position and clamping components together utilizing various structures exerting inwardly directed compressive forces or the like have been utilized. Typical of such structures are those shown in prior art U.S. Pat. Nos. 5,473,298 and 5,679,989. While such structures operate relatively well, they require a large number of parts and once assembled and placed into operation cannot be readily maintained or repaired without complete disassembly and in many instances are difficult to adjust at the time of manufacture to provide the required operational stability.
In accordance with the present invention, there is provided a torque motor having a base, upper and lower pole pieces, first and second permanent magnets disposed between the pole pieces, a pair of electromagnetic coils positioned about the ends of an armature carried by the base and a pair of shims sandwiched between the lower pole piece and the base. Each of the base and pole pieces define openings therethrough while the shims and the pole pieces define slots or grooves therein. The holes, slots and grooves are aligned with each other and a plurality of fasteners are positioned through the openings, slots and grooves and are threaded into openings provided in the base. After the component parts are properly adjusted to provide mechanical and magnetic null, the fasteners are secured to maintain the components of the torque motor in properly aligned operational position.